I made a amazing discovery. If this mothership ( which is capable to reach orbit ) is reloaded for its main tank and also given 30 tons of cargo it could also reach planet MARS, but not only Mars...it could land there at the speed of 200 km/h. Landing empty the speed needs to be just 160 km/h.

This is due to the 1/3 gravity but also the 1/3 space shuttle wing loading.

This is really the most minimalist craft to Mars...but since it gets only to LEO with SRB system ( TSTO ) it has to start travelling from there to Mars and it takes time months more than going faster with chemical rockets. But this could feed the people on the ISS or T-Bird one if that is left to orbit for some reason.